The invention relates to a system to control the motor drive of a garage door panel which is reciprocatingly movable and guided along a predetermined track between two end positions, and possibly one or more intermediate stop positions, said garage door panel including switching devices which indicate the assumption of the respective end position or stop positions, the output signals of these switching devices being usable to switch off the power supply to the drive motor, wherein the limit switches or reference point switches are actuatable through rotatable cams which simulate the garage door path.
Systems of this type by which the garage door panel's path of motion is simulated are already known. Here, a motion variable corresponding to the motion of the garage door panel, and derived from its drive, is subject to a high reduction in gear ratio and utilized to rotate a cam, the motional path of which reproduces the actual measured distance of the moved garage door panel. This cam which functions as the simulator element, in other words, also moves between two end positions corresponding to those of the garage door panel, at which positions it actuates switching devices which thus reproduce the two end positions of the garage door panel. In addition to the end positions, any desired intermediate stop positions for the garage door panel may be attained.
A simulator of this type, which may be preferably disposed in the region of the drive or of the drive control, is in fact, protected from damage, contamination and moisture. After installation of the garage door, however, the simulator requires an especially precise position adjustment corresponding to the garage door—for example, in such a way that the start of the path of motion for the garage door panel must exactly match the start of the displacement path of the simulator. Given the high path transmission ratios here, even small deviations result in the danger that the garage door panel will be driven beyond its end positions, thereby colliding with a guide or other object, or that the desired intermediate position for the garage door panel will not be precisely attained. So-called zeroing between the garage door panel and the rotating cam thus requires particular care and sensitivity. The various cams for the reference points End Position Up, End Position Down, or the intermediate positions are usually located on a shaft which is linked through a reduction gearing to the gear unit. A known approach is to adjust the cams using a tool such as a hex key wrench. However, the necessary sensitive and precise adjustment for the precision-mechanical system presents certain problems. These problems are further aggravated by the fact that the drive units are generally installed several meters above ground level.